The benchmark 30-year fixed-rate mortgage fell 7 basis points this week, to 4.81 percent, according to the Bankrate.com national survey of large lenders. A basis point is one-hundredth of 1 percentage point.

That 4.81 percent is a record low in the nearly 25-year history of Bankrate's weekly survey. For the previous two weeks, the benchmark 30-year rate had stood at 4.88 percent, and that had been the record low.

According to records kept by the National Bureau of Economic Research, rates of FHA-insured mortgages averaged 4.81 percent in June and July, 1956, and 4.78 percent that May. That seems to be the last time rates were lower than now.